A recent study found veterans with PTSD experienced fewer nightmares when they received treatment for their obstructive sleep apnea.

Obstructive sleep apnea is a sleep disorder in which an individual's airways get blocked. The person is unable to get enough oxygen during the night and frequently stops breathing for short periods.

The reasons for the reduced nightmares were not clear.

But one thing was clear: the more closely the veterans followed their doctors' instructions in treating their sleep apnea, the fewer nightmares they had.

"Ask your doctor about treating sleep apnea."

This study, led by Sadeka Tamanna, MD, a specialist in sleep medicine at the University of Mississippi Medical Center in Jackson, aimed to find out whether treating veterans' sleep apnea also improved their nightmares from PTSD.

The researchers looked through the records of all veterans treated at a Veterans Affairs medical center sleep clinic between May 2011 and May 2012.

The researchers analyzed the medical records of those veterans who had both obstructive sleep apnea and PTSD.

The veterans underwent sleep studies in which the researchers learned whether their sleep apnea symptoms occurred primarily during REM sleep or non-REM sleep.

CPAP treatment involves wearing a mask that pushes air into the patients' airways to make sure they get enough oxygen.

In analyzing the results, the researchers took into account how well the veterans followed their treatment plan, which was based on how many nights they used the CPAP for at least four hours.

The results showed that the average number of nightmares in both groups (REM-related and non-REM-related sleep apnea) fell when the veterans were regularly using their CPAP.

The better the men complied with their CPAP treatment while asleep, the fewer nightmares they reported experiencing.

The patients in the non-REM-related group had better compliance than those in the REM-related group.

While 75 percent of the veterans with non-REM-related sleep apnea used their CPAP regularly, 56 percent of those with REM-related sleep apnea did.

The researchers concluded that treating veterans' sleep apnea with CPAP also helped reduced their nightmares if they had PTSD.

William Kohler, MD, the director of the Florida Sleep Institute in Spring Hill, and a dailyRx expert, found these results particularly interesting because of what is known about dreaming and REM.

Normally, it is during REM sleep that individuals dream, and "...treating sleep apnea, theoretically, would increase the REM sleep," Dr. Kohler said.

However, he noted, "Sleep apnea would tend to cause awakenings, and reducing awakenings would tend to decrease the remembrance of dreams from PTSD."

Therefore, it may be that individuals remember fewer of their dreams when their sleep apnea is treated because they wake up less often during REM sleep.

There are, however, other possible mechanisms that might explain why treating sleep apnea with CPAP would also help reduce nightmares from PTSD.

"It may be that the stress of the sleep apnea contributes to the nightmares," Dr. Kohler said. "I have patients that tell me that part of their nightmares at times is feeling like they are drowning or suffocating, which in reality is what's happening during sleep apnea."

A person whose sleep apnea is treated is no longer struggling for oxygen while asleep, so that may help in reducing nightmares.

Dr. Kohler noted that research already exists to show that treating sleep apnea can also improve patients' mental health.

In fact, getting enough quality and quantity of sleep improves mental health, and treating sleep apnea can help in both of those departments.

"It's just so fascinating all the things we're learning that treating the sleep process can do to us in terms of our behavior and functioning, let alone our physical health," Dr. Kohler said.

This study has not yet been published in a peer-reviewed journal. The findings are therefore preliminary.

The study was presented at SLEEP 2013, the 27th annual meeting of the Associated Professional Sleep Societies LLC.

Information regarding funding or conflicts of interest was not provided.

Post Traumatic Stress Disorder (PTSD)

PTSD is an anxiety disorder that some people get after seeing or living through a dangerous event. Approximately 11 million people in the United States suffer from post-traumatic stress disorder. PTSD occurs when an individual...